Do Universals Exist? Think of all of the red roses that you have seen in your life. Obviously each of these flowers had the property of being red they all possess the same attribute (or property). The attribute that they all have in common is referred to by the term redness. Redness is an example of a universal, in this case an attribute that is shared by a variety of particular things. There are also universals corresponding to particular relations, like the father of and between, and particular types of thing, like glass and beer. The debate concerning the existence of universals centers on whether universals, like redness, refer to anything. Realists contend that they do refer to something, whereas nominalists contend that they are merely linguistic objects that are useful for the grouping of a variety of similar things all that exists are the particulars. Realism One of the considerations that motivates some to take a realist position is the claim that in order to have an account of why the sentence Alice s blood is red is true, both Alice s blood and red must refer to something. On such a view Alice s blood refers to the blood in Alice s body and red refers to the universal redness. You might wonder, however, what exactly do universal terms refer to?
There are different possible answers to this question. A common account is that that the term redness refers to the attribute that is exemplified in a variety of different particulars. That is, the same universal is jointly exemplified (or instantiated) in a variety of spatiotemporally separated objects. The universal refers to a particular attribute that each of these objects have in common. The same single universal is exemplified in each of the different instances in which it appears. What would be some examples of a single universal exemplified in a variety of different objects? Here are some others. Many distinct cars exemplify the same shape, for example each mini cooper has the same shape. Many CD s exemplify the same (collection of) music and many distinct birds exemplify the same song. And many different pairs of mother and child exemplify the same parental relation. You get the idea Plato s realist account, however, is different. Like the previous account, Plato contends that universals are actually existing things, which are exemplified in particular instances, but he also contends that they exist eternally in a non-spatiotemporal world distinct from our spatiotemporal world. Plato calls these universals Forms. The Form corresponding to a particular attribute is, according to Plato, the cause of the appearance of the Form in any particular instance. It s not entirely clear in what sense the Form causes the appearance.
Gould and Mulvaney summarize an argument that Plato gives for the existence of the Forms: We have knowledge of objects, such as perfect circles, that cannot be based on anything we have sensed. Knowledge must have an object. Therefore there must exist some other entities (the [Forms]) distinct from those of the senses. (335) There are forms for colours, Forms for shapes, Forms for mathematical objects (numbers, lines, etc.), Forms for relations, and, importantly, Forms for virtues (justice, courage, goodness). Consider the case of an ordinary billiard ball. How might Plato explain its existence/appearance? With some understanding of Plato s theory of the Forms, we may examine Plato s epistemological system. The first thing that Plato does to describe this system is to draw an analogy between the Sun and the Form of the Good. Just as the Sun is the cause of all our knowledge of the visible world, the Good is the cause of all our knowledge of the intelligible world. The illumination from the Sun reflects off of physical objects and enables us to know them. In a similar way the Good illuminates knowable things (cf. physical objects) with truth and reality (cf. light) the intelligence (ie. mind/soul?) to possess knowledge and understanding. What could Plato mean by the intelligible world?
The second analogy the Plato uses is the divided line. This is used to express the variety of visible and intelligible knowledge. The line (segment) represents all knowledge. It is perhaps best to think of this as a vertical line. Plato divides this into two (unequal) parts, one (the bottom part) corresponding to visible knowledge and the other (the top part) corresponding to intelligible knowledge. The bottom part is subdivided into two (unequal) parts. The lower part represents knowledge of things such as images and shadows, which corresponds to the faculty of imagination. Think of the knowledge of a forest that you could gain on a moonlit night. Such knowledge occurs when the Sun weakly illuminates physical objects. The upper part represents knowledge of the physical objects themselves, which corresponds to the faculty of belief. Such knowledge occurs when the Sun clearly illuminates physical objects. (see second last page of this document for diagram)
The top part is also subdivided into two (unequal) parts. The top part represents knowledge of the Forms, which corresponds to the faculty of Knowledge or Understanding. Such knowledge occurs when the Good is strongly present. The stronger the presence of the Good, the clearer and truer the knowledge of a Form is. How to understand the bottom part is less clear (and is a subject of debate). One way we could think of it, which will suit our purposes here, is that it is being used to represent the view of the physical world implied by our scientific understanding, which corresponds to the faculty of thinking. Such knowledge occurs when the Good is only weakly present. (see the last page of this document for (corrected) diagram)
The kind of thought distinctive of the upper part is reasoning from premises and hypotheses down to different conclusions. This is characteristic of scientific and mathematical knowledge. The kind of thought distinctive of the upper part is working from hypotheses and moving up to first principles using the Forms as a guide. The method to be used to achieve this kind of knowledge is a method called dialectic. To give a (not necessarily faithful) example of how dialectic works, we may think of this as the process used to generate new scientific theories. A hypothesis is made and tested. If it is not confirmed, we adjust our hypothesis, which we then test. This, if unconfirmed, will lead to some adjustment of the adjusted hypothesis, and so on. The idea is to move up to some principle that has the highest degree of truth and, consequently, will never be disconfirmed. (For a variety of reasons this is not how philosophers of science view the way in which scientists actually develop new theories. But that s another story )
Nominalism With what time we have left, let us turn to the opposing view to realism nominalism. According to a nominalist, there are only particulars. In our excerpt, Hume enters into the debate by considering whether abstract or general ideas are general or particular in your mind s conception of them. Thinking back to Locke s account of the development of general ideas, we saw that he accounted for the development of such ideas by showing that we develop them by seeing that a single term can be used to refer to a variety of individuals. Hume accounts for this by observing that we develop general ideas by abstracting particular (sets of) properties possessed by a variety of particulars. That set of properties can be then be used to refer to the set of particulars that share that set of properties. For example, the abstract idea of a person represents people of all sizes and all qualities, but it doesn t represent simultaneously all sizes and qualities nor does it represent no particular at all. Since we can have an idea of the possible sizes and qualities of different people, we are able to usefully use the term person conversation and thought. So can we have in our minds the concept of a general person, in abstraction from our ideas of particular people?
Think of the concept tree. What comes to your mind when you think of this concept? Similarly, think of the concept person. What comes to your mind when you think of this concept? We will give the same kind of answer that we give in these two cases when we consider any particular concept. According to Hume, the consideration of a general term is a readiness to survey any of the objects to which the term applies. This explains how some ideas are particular in their nature, but general in their representation. (348) When we consider a general term, we develop a habit to think of a particular object, and then a habit to think of any other particular object, and so on. We also by habit restrict our thinking to a subset of the objects referred to by the general term. In the case of trees, for example, when we move in thought through different particular trees we only think of some kinds of trees. Even though we don t think of all kinds of tree, however, we are still able to use the term tree correctly. Well, for any given term we will at least be able to use the term correctly in a wide variety of, most, or almost all, cases. Hume uses the term geometric figure as an example. In this case we always consider particular figures (circles, squares, triangles, parallelograms, etc.) and we never consider all the figures but are able to call forth an appropriate individual for a given case as required (provided enough familiarity with the objects).